Add VESA capabilities to an old HP 23xi monitor. You need to disassemble the stand and retrieve the metal piece and mount it to the printed part. You also need to make 4 holes in the back plastic of the monitor (disasseble the screen first) to secure the printed piece using 4 long M3 screw.

Optionally you can just use the metal piece without making holes in the plastic (not tested) but the added rigidity with the 4 screws is noticeable.